Chapter 29: Plant Diversity

1. Chapter 29: Plant Diversity How Plants Colonized Land By: Meg Riley, Anna Ferlanti, and Laurie VanBenschoten

2. The Greening of Earth • Land plants evolved from aquatic green algae 500 mya • Plants are crucial to life on Earth • Supply Oxygen • Provide Habitats • Provide Food Charophyceans (algal ancestor of land plants) http://greatneck.k12.ny.us/GNPS/SHS/dept/science/krauz/bio_h/images/29_03Charophyceans_LP.jpg

3. Evolution from Algae • Aquatic green algae= charophyceans • closet living relative of land plants, share a common ancestor • First land plants were seedless • reproduced using spores

4. Evidence for Common Ancestry • Morphological and Biochemical Evidence • Structure of flagellated sperm • Closely resembles that of charophyceans • Genetic Evidence • Nuclear & chloroplast genes suggest relatedness to charophyceans • Confirms conclusions from above

5. Adaptations for Movement to Land • Adaptations enabling the Move to Land • A chemical found in both charophyceans & land plants Algae prevents zygote from drying out in exposed environments Plants encases spores

6. The Plant Kingdom • Kingdom Plantae currently includes all embryophytes • Embryophytes= plants that grow from an embryo • excludes charophyceans

7. Derived Traits of Land Plants • These traits, unique to nearly all plants, distinguish them from charophyceans • Apical meristems- localized regions of cell division that make vascular tissue • Alternation of generations- alternation between two multicellular body forms between generations • Walled spores produced in sporangia- multicellular capsules that contain and protect spores during development • Multicellular gametangia- multicellular organs in which gametes are produced • Archegonia- female, 1 egg • Antheridia- male, many sperm • Multicellular, dependent embryos- zygote retained within tissue of female parent and develops with nutrients from mother • Cuticle coverings- layer of polyesters & waxes that prevents plant from drying-out ***(see pg. 576-577 for full explanations)

8. Evolutionary History of Land Plants

9. Gametophyte vs. Sporophyte Gametophyte multicellular haploid form of a cell undergoing alternation of generations 1n Sporophyte multicellular diploid form of a cell undergoing alternation of generations 2n VS.

10. Characteristics of Bryophytes • Bryophytes are seedless nonvascular plants • found in three plant phyla…phylum Hepatophyta (liverworts), Anthocerophyta (hornworts), and Bryophyta (aka moss) • Gametophyte is dominant over sporophyte • Bryophyte Gametophytes • Characteristics • Form ground-hugging carpets, low to the ground, short • Thin, approx. 1 cell layer thick • Bryophyte Sporophytes • Consist of 3 parts: • Foot- anchors to set into sporophyte • Seta (or stalk)- holds up sporangium • Sporangium (or capsule)- contains & protects spores • Ecological and Economic importance of Mosses • Mosses are widespread and important • Ex. Peat moss used as fossil fuel and good for preserving bodies in swamps

11. : http://www.youtube.com/watch?v=jcWYAnmm-QE

12. Life Cycle of Bryophyte (ex. Moss) • Spores develop into threadlike strands of plant fibers • The haploid strands produce “buds” that grow into gametophytes • Most mosses have separate male and female gametophytes with antheridia and archegonia respectively • A sperm swims through a film of moisture to an archegonium and fertilizes the egg • The diploid zygote develops into a sporophyte embryo within the archegonium • The sporophytes grows a long stalk, or seta, that emerges from the archegonium • Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte • Meiosis occurs and haploid spores develop in the sporangium of the sporophyte • Sporangium pops off, propelling spores into the air using “teeth”

13. Characteristics of Lycophytes & Pterophytes • Origins and Traits of Vascular Plants • Life Cycles with Dominant Sporophytes • More sporangia, more spores, more evolutionarily fit to survive into adulthood • Transport in Xylem and Phloem (type of vascular tissue) • Xylem-conducts water & minerals • Phloem- conducts sugar, amino acids, and other organic products • Evolution of Roots • Roots –anchor plant, allow for absorption of water and nutrients from soil • Evolution of Leaves • Leaves- increase surface area, allow capture of more sunlight for photosynthesis, increase plant efficiency • Mircohpylls- leaves of old lycophytes • Megaphylls- leaves of new lycophytes, more complex

14. Characteristics of Seedless Vascular Plants (cont.) • Sporophylls and Spore Variations • Sporophylls (modified leaves with sporangia) • Homosporous vs. Heterosporous • Megaspores vs. Microspores

15. Life Cycle of a Lycophyte (ex. Fern) • Sporangia release spores • Spore develops into photosynthetic gametophyte • Cross or self- fertilization may occur between male and female gametes • Sperm use flagella to swim from antheridium to archegonium • Sporophyte grow out of archegonium of gametophyte • Spores form in clusters on underside of reproductive leaves (sorus)

16. Classification • Phylum Lycophyta: older seedless vascular plants, common ones include spike & club mosses (not true mosses) • Phylum Pterophyta: younger seedless vascular, all sorts of ferns Spike/Club Moss Fern http://kmacphoto.net/ferns.jpg http://www.sd23.bc.ca/~mbirkela/FOV1-000ABDA6/S0A59B017.4/tips-for-sorting-through-ferns0.jpg

17. Significance • How evolution of vascular tissue, roots, and leaves allows plants to grow bigger than ever before…development of large forests • Increased removal of CO2 from atmosphere, resulting in global cooling • Plants fossilize to from coal, however, once coal is burned as fossil fuels, it results in global warming

18. Answers to Activity: • Part 1- Moss 5 2 6 3 1 7 8 4 • Part 2- Fern 2 6 3 4 1 5